Roxanne Duff told police the Rottweiler had run away at that point. But the dogs' owner, neighbor Shawn Lerch, suspected foul play.

The Leechburg, Pa., man told cops his neighbors had returned the golden retriever mix but not the Rottweiler puppy. He suspected the Duffs had kept the Rottweiler.

When police confronted the Duffs, Scott said that the puppy had run away. But when cops returned the next day, the Duffs' young son told police "his mommy had given the dog to a woman from the Internet," according to NBC News.

Police confronted Scott Duff about this, and he said he knew nothing about it. But he later called police back to say his wife had indeed sold the dog on Craigslist.

She allegedly got $50 for the Rottweiler.

The problem with this money-making scheme is that taking someone else's property is theft, and selling stolen property is just as illegal as taking it in the first place.

Both Scott and Roxanne Duff were charged with conspiracy as well as false reporting and not returning lost property. The latter is a subset of theft.

Conspiracy is an interesting crime because it requires at least two people who plan to do something illegal. There cannot be a conspiracy of one to commit a crime.

By charging the Duffs with conspiracy, prosecutors appear to suspect that the husband and wife worked together to sell the puppy on Craigslist.

The woman who bought the puppy didn't know it was stolen but she returned it to its rightful owner. The Duffs, meanwhile, will have to answer for their alleged crimes when they show up in court next month.